The instant invention relates generally to fluid heat exchanger apparatus adapted for exchange of heat between flowing streams of fluid, and in particular to vertical counterflow heat exchangers which can be employed as air-to-air or air-to-water heat exchangers. The present heat exchanger apparatus is especially useful in cooling hot exhaust air with cold water for energy conservation and condensation of air pollutants, in cooling hot water with cold ambient air, or in cooling hot ambient air with cold water for air conditioning.
The heat exchanger of the present invention is of the counterflow type including first and second sets of passages separated by heat exchanger plates. Such heat exchanger is supported so that the passages extend substantially vertically. When used as an air-to-water heat exchanger, water is sprayed onto the surfaces of the upper ends of one set of passages and flows down their length, while air is transmitted into the bottom ends of the other set of passages and flows up their length on opposite sides of the heat exchanger plates. This results in an extremely efficient heat exchange operation through the exchanger plates separating the two sets of passages.
It has been known to spray water into one set of passages in air-to-air heat exchanger, as shown in U.S. Pat. No. 1,409,520 of Bird and U.S. Pat. No. 2,825,210 of Carr. In the former patent the heat exchanger is horizontal and the water is sprayed in the outlet end of one set of air passages so that the water does not flow down the length of the passages. In the latter patent the heat exchanger plates are supported by rubber spacers which separate the two different sets of passages so that there is no appreciable direct lateral transfer of heat through the thickness of the separating members in the manner of the counterflow heat exchanger of the present invention.
The present air-to-water heat exchanger apparatus has the advantage that the exit temperature of the air being cooled or of the water being heated can be easily controlled by adjusting the water flow or air flow with a valve or damper which may be automatically operated by a temperature sensor. Another advantage is that the apparatus is reversible and can also be used for cooling hot water and warming cold air without modifications in the heat exchanger. In addition, the high latent heat of steam or moist exhaust air can be recovered by transfer to clean water flowing through other passages in the exchanger for heating buildings or other uses.
Finally, hydrocarbon vapors and other air pollutants can be removed from hot exhaust air by condensing such pollutants within the passages of the heat exchanger. When the condensed pollutants remain in a liquid state, they will run down the vertical passages and out of the exchanger apparatus through a drain. However, if such condensed pollutants tend to solidify as a deposit on the surfaces of the passages, they may be removed by injecting solvents or cleaning agents into the air flowing through such passages. In addition, solid particle pollutants can be removed from the air by depositing water or a more viscous liquid, such as oil, on the surface of the passages to collect impinging particles and remove them with the collecting liquid.
Counterflow heat exchangers have been proposed, such as in my earlier U.S. Pat. No. 3,381,747, comprising a series of heat exchanger plates disposed within a housing defining a multiplicity of channels or passages extending side-by-side along the housing and constructed so that fluid flowing in alternate ones of the channels exchanges heat with the fluid flowing in the remainder of the channels. To be efficient, the exchanger plates defining such channels should have large surface expanses exposed to the fluids passing through the exchanger. Toward these ends, I have found that thin metallic sheets of considerable width, and preferably corrugated to increase the turbulence of fluids passing through the exchanger, may be utilized in producing a highly satisfactory exchanger of many types of applications. In addition the heat exchanger of the present invention further differs from that of my earlier patent and the non-counterflow heat exchanger of U.S. Pat. No. 3,371,709 of Rosenblad by its simple and economical split end construction. Thus, the ends of the heat exchanger plates are split into two end portions which are joined to different exchanger plates on opposite sides thereof to form the two sets of passages. This provides a more efficient heat exchanger which is capable of handling an extremely large amount of air flow in the range of hundreds of thousands of cubic feet per minute.
In the manufacture of such an exchanger, because of the flexible nature of the plates or sheets making up the exchanger plates, and the great number of plates which ordinarily make up a typical exchanger, there are certain problems presented in assembling the unit with the plates properly positioned in a permanent manner within the exchanger, and with the completed unit having the desired strength and rigidity. To be kept in mind also is any method utilized in making the exchanger should be one which lends itself to be performed without the need of using highly trained personnel, and in a quick and expeditious manner. These problems are overcome by the present invention.